Rare earth metal benzyl complexes bearing bridged-indenyl ligand for highly active polymerization of methyl methacrylate

Abstract

The novel anionic bridged-indenyl rare earth metal benzyl complexes [{C 9H 6SiMe 2(CH 2) 2SiMe 2C 9H 6}Ln(CH 2C 6H 4- p- t Bu) 2][Li(THF) 4] (Ln = Y ( 1), Lu ( 2)) were synthesized by an acid–base reaction of C 9H 7SiMe 2(CH 2) 2SiMe 2C 9H 7 with one equiv. of rare earth metal trisbenzyl complexes, which were formed in situ from the reaction of anhydrous LnCl 3 with LiCH 2C 6H 4- p- t Bu in 1:3 molar ratio in THF. The complexes were characterized by elemental analysis, NMR spectroscopy, FT-IR spectroscopy, and X-ray structural analysis in the case of 2. Both complexes are active for the polymerization of methyl methacrylate (MMA) to afford high molecular weight and narrow molecular weight distribution PMMA. The molecular weights of PMMA could be controlled using 1 as a polymerization initiator in chlorobenzene at −40 °C.